This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We have developed a new method for solving photon transport problems that combines accuracy and increased speed when compared with conventional Monte Carlo simulations. This ?condensed history? method adapts a strategy routinely used to solve charged transport problems for radiation dosimetry, problems that would be prohibitively costly to solve conventionally. This method promises to be especially useful for tissue problems calling for computational models intermediate between classical diffusion theory and rigorous radiative transport. Gains in computational efficiency by factors of 4-5 over conventional simulation can be expected in many instances.